Current flow mechanisms have been studied for liquid phase epitaxy grown isotype heterostructures lattice-matched to GaSb substrates. The dark current mechanisms in the N-n isotype heterostructures were investigated in detail at several temperatures. It is shown that both the type II staggered and misaligned heterojunctions can behave as Schottky diodes and the dark current-voltage characteristics of this isotype heterostructures were rectifying over the whole temperature range 90-300 K. These measurements establish that the reverse current in both (staggered and misaligned) investigated structures are determined mainly by tunneling mechanism. The theoretical relations for reverse dark current in staggered lineup isotype heterostructures have been developed. (C) 2007 Elsevier B.V. All rights reserved.